The recent development of low loss single mode optical fibers with low dispersion at the 1.3 and 1.6 micron wavelengths has focused attention on long-wave integrated optical circuits and optical systems that couple to such fibers. Such optical circuits and systems are useful in telecommunications, data communication, optical signal processing, optical interconnection, optical sensing, and microwave antenna control applications. Semiconductor guided-wave circuits are of special interest because they can, in principle, provide optoelectronic integration; i.e., the monolithic integration of optical guided-wave components with electronic circuits and electrooptical components on a single chip.
The fundamental building blocks of such guided-wave circuits are the channel waveguides which are used to make various optical components including switches, modulators and interconnects. In all these components, it is essential to keep optical propagation losses at a minimum in order to allow multiple guided-wave components to be cascaded on one wafer without incurring a significant loss penalty.
Waveguides suitable for use in an integrated optical circuit due to their high efficiency, small size and ease of fabrication are described in our related application entitled, "Method of Fabricating Low Loss Crystalline Silicon Waveguides" (Joseph P. Lorenzo and Richard A. Soref) Ser. No. 928,349 filed Nov. 10, 1986. The method described therein provides the desired techniques for fabricating waveguides operative at 1.3 to 1.6 micron wavelengths which do not suffer from the complexity or expense of fabricating waveguides using binary, ternary or quaternary alloy compositions of various materials. In another related application, entitled "Electrooptical Silicon Devices" (Joseph P. Lorenzo and Richard A. Soref) Ser. No. 036, 822 filed Mar. 26, 1987, various silicon devices compatible with the above mentioned waveguides have been described. Other related applications include "Electrically Controlled Integrated Optical Switch" (Richard A. Soref) Ser. No. 050,358 filed May 18, 1987 now U.S. Pat. No. 4,746,183 and "Silicon Waveguide with Monolithically Integrated Schottky Barrier Photodetector" (Andrew C. Yang, Joseph P. Lorenzo and Richard A. Soref) Ser. No. 049,352 filed May 14, 1987 which describe switching and light modulating silicon devices that can be suitably integrated, manufactured and networked with low loss silicon waveguides. In addition, the last mentioned application describes an integral photodetector for use with low loss silicon waveguides. The above components allow for the routing and manipulation of optical signals as well as their conversion to electrical pulses. In view of the above, there still remains the problem of integrating conventional light emitting diodes (LEDs) and lasers with silicon waveguides.
Conventional LEDs rely on III-V compounds and the propagation of light through free space to drive signals through waveguides. In addition, intimate coupling of silicon waveguides with conventional light emitting diodes has proven to be a difficult manufacturing task and unsuitable for standard manufacture of integrated optical circuits. In general, many of these conventional optical devices require special facets or exotic growth techniques which result in a relatively high cost of manufacture. This effectively prevents the placing of conventional laser and light-emitting diodes within integrated optical circuits.
A need therefore exists for an improved light-emitting diode suitable for use in integrated optical circuits and particularly optical circuits utilizing silicon waveguides.
A further need exists for a light-emitting diode suitable for intimate coupling with silicon waveguides and which is suitable for use where desired in integrated optical circuits.
Finally, the need exists for an inexpensive light-emitting diode for use with integrated optical circuits.